Pea plants form seeds inside pods. A single gene controls the colour of pea pods. Some pea pods are green and others are yellow. The allele for green is dominant and is shown by the letter G. The allele for yellow is recessive and is shown by the letter g. Fig. 5.1 shows a pedigree diagram of pod-colour inheritance in some pea plants. Key: shaded circle means green pod; unshaded circle means yellow pod. Individuals 1-7 are shown.
(a)[2]
Describe what the term allele means.
(b)[4]
Determine the genotypes of individual 1 and individual 2 in Fig. 5.1. Explain how you determined your answer for each individual.
(c)[3]
Complete the Punnett square to determine the possible offspring genotypes and calculate the expected phenotypic ratio. The expected phenotypic ratio for the offspring is [BLANK] green pods : [BLANK] yellow pods.
Worked solution & mark scheme
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